Type member position sensing system in a high speed printer

ABSTRACT

A PRINT HAMMER ACTUATOR ASSEMBLY FOR HIGH SPEED A POSITION SENSING SYSTEM THAT DETECTS THE LOCATION OF EACH ELEMENT OF A PLURALITY OF ELEMENTS AS THEY TRAVERSE A PRINTERS. TWO ELECTROMAGNETICALLY ENERGIZED ACTUATOR CONSTRUCTIONS ARE PROVIDED, WHICH ARE MECHANICALLY EQUIVAPREDETERMINED PATH. THE SYSTEM IS DISCLOSED IN CONJUNCLENT BUT OF COMPLEMENTARY GEOMETRY SO THAT THEY CAN BE TION WITH A PRINTING ARRANGEMENT WHEREIN THE ELEMENTS ARE THE CHARACTER BEARING FINGERS ON A CONTINUOUS MOVING LOCATED TOGETHER IN A MANNER FACILITATING INDIVIDUAL REMOVAL OF THE ACTUATORS. THE ACTUATORS ARE LOCATED IN DIBELT. RECTIONS PARALLEL TO THE LINE OF PRINT BY ALIGNMENT COMBS FASTENED TO A BASE PLATE, AND LOCATED IN DIRECTIONS NORMAL TO THE LINE OF PRINT BY STOP BARS FASTENED TO THE BASE PLATE. 611

20, 1,71 5 McDQwELL EIAL 3,605,610

TYPE MEMBER POSITION SENSING SYSTEM IN A HIGH SPEED PRINTER Filed June4. 1968 4 Sheets-Sheet l I8 I I8 I '/7//////A m m 7///////A m m mm 3sHG3LEISEQG THEIR ATTORNEY Sapt. 20, 1971 E. B. M DOWELL ETAL TYPE MEMBERPOSITION SENSING SYSTEM IN HIGH SPEED PRINTER Filed June 4. 1968 4Sheets-Sheet a ODD DRIVE INTERVAL INTERVAL EVEN COMPARE INTERVAL 1,

EVEN

ODD|

VOIJ'AGE 4- WIDE FINGER 'H TIME I DARK I INTERVALS I I 'r INVEN EARLE B.M DOWELQ CLIFFORD M. JONES BY SEYMOUR M DePUY THEIR ATTORNEY 4Sheets-Sheet 3 lNVbNTOR Ems? 747M M EARLE E. B. M DOWELL ETAL TYPEMEMBER POSITION SENSING SYSTEM IN A HIGH SPEED PRINTER Filed June 4.1968 o 06 F586 z c385 E0352 E E9; mm E mfism h. QzoEBd w mm; Q wo mwozmr mom 6m Sept. 20, 1971 THEIR ATTORNEY 55. 26, 1 99 1 MCDOWELL M3,605,610

TYPE MEMBER POSITION SENSING SYSTEM IN A HIGH SPEED PRINTER Filqd June4.. 1968 I 4 Sheets-Sheet L F aa INVENTOR EARLE a. mcoowsu. CLIFFORD M.JON

BY SEYMOUR M. De

THEIR ATTORNEY n MU C Lm .uC U

United States Patent 3,605,610 TYPE MEMBER POSITION SENSING SYSTEM IN AHIGH SPEED PRINTER Earle B. McDowell, Clifford M. Jones, and Seymour M.

De Puy, Waynesboro, Va., assignors to General Electric Company FiledJune 4, 1968, Ser. No. 734,500

Int. Cl. B41j 5/30 U.S. Cl. 101-93 15 Claims ABSTRACT OF THE DISCLOSUREA position sensing system that detects the location of each element of aplurality of elements as they traverse a predetermined path. The systemis disclosed in conjunction with a printing arrangement wherein theelements are the character bearing fingers on a continuous moving belt.

BACKGROUND OF THE INVENTION The rapid expansion of the data transmissionfield has brought with it the need for high-speed printing devices thatcan accept input data at a high rate. United States patent applicationSer. No. 734,501, filed June 4, 1968, by Earle B. McDowell and CliffordM. Jones, and assigned to the General Electric Company, discloses animproved partial line-at-a-time type printer which provides a rapidprintout of data. The apparatus of the cited copending patentapplication utilizes a continuously moving character belt that carriesthe typefaces for each character to be printed. The number of typefacescarried on the belt depends upon the number of characters or symbols theapparatus is to be capable of printing. A plurality of hammers arearranged in a row across the face of a record medium such as paper, theposition of each hammer establishing a column in which a character maybe printed. An inking ribbon is positioned in front of the record mediumand the path of the character belt is located behind the inking ribbonand in front of the hammers.

If the format of a page provides for a line length of eighty characters,this means that the printer must be capable of printing any desiredcharacter in any one of eighty columnar positions. Means must beprovided for discretely indicating to the control circuitry where eachcharacter appears relative to the record medium. When this is known,circuitry may be provided for energizing the hammers at an appropriateposition to imprint the appropriate characters in any desired position.The lineat-a-time aspect of the apparatus is achieved by rotating thetype carrying belt at a speed which permits presentation of eachcharacter at each of the column positions within the time required forreceipt of an entire line of data information.

With this type of printing system, it is necessary to know the positionof each character at any instant of time. Since the relative position ofeach typeface on the belt is fixed, it is possible to simply establishthe position of a particular or reference character or type bearingfinger on the belt and extrapolate from this information. When thisparticular character is detected at a predetermined point or referencecolumn location on the complete path of the belt, a font signal isgenerated and the font signal is used to initiate circuit operationsthat ultimately result in the proper operation of the various typehammers.

3,605,610 Patented Sept. 20, 1971 ice Since the movement of thecharacter belt is subject to slight variations in speed, it is alsodesirable to generate a signal that reflects the velocity of beltmovement. More precisely, a pulse is generated each time any characterpasses a particular point on the path of the belt. The repetition rateof these pulses corresponds to the velocity of the belt and theirrelative timing discretely represents the relative position of thecharacter.

SUMMARY OF THE INVENTION The present invention relates to a controlsystem for use with a partial line-at-a-time type printers; moreparticularly, it relates to a control system for generating signalsdiscretely representative of the relative position of the characters ona character belt and the columns on a record medium.

The illustrative embodiment of the invention described hereinafter,operates in conjunction with a character belt wherein the typeface foreach character is located at one end of a flexible finger. The fingersproject at right angles from equi-spaced positions on the body of thebelt and in general are of identical form. The belt is normally mountedon drive devices which rotate about parallel axes at each edge of therecord medium. Thus, the fingers move along a linear path across a lineon the record medium.

An object of the invention is to provide improved means for detectingthe position of individual elements traversing a predetermined path.

Another object of the invention to provide an improved means fordetecting the position of individual characters on a continuously movingcharacter carrying device.

Another object of the invention is to provide an improved arrangementfor monitoring passage of an element of known dimensions past apredetermined point along its path.

Still another object of the invention is to provide an improved systemfor generating discrete signals upon approach and departure of anelement relative to a predetermined position.

Yet another object of the invention is to provide an improved system forgenerating signals upon passage of a plurality of elements past apredetermined point and for generating an additional discrete signalwhen the characteristics of one of said elements differs from those ofthe other elements.

In accordance with the invention, there is provided an improved positionsensing system operative to establish the precise location of individualelements in a plurality of elements traversing a predetermined path,comprising first and second sensing means positioned proximate to thepath which are separated by a discrete distance, and means for modifyingthe output of the sensing means upon approach and departure of eachelement.

A complete understanding of the invention and a fuller appreciation ofits obejcts and features will be available from the following detaileddescription which is made in conjunction with the drawings of aparticular illustrative embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative sketchshowing one type of partial line-at-a-time printing apparatus adaptedfor utilization of the present invention;

FIG. 2 is a view of a photoelectric pickup structure embodying theprinciples of the invention;

FIG. 3 is a view similar to FIG. 2, showing another embodiment of theinvention;

'FIG. 4 comprises a plurality of waveforms illustrating the voltageconditions at various points in the circuitry of a further embodiment ofthe invention;

FIG. 5 is a block diagram of circuitry employed for developing a printcontrol circuit in accordance with the invention;

FIG. 6 is a chart showing the positions of various fingers with respectto the control functions that are initiated by the circuitry of FIG. 5at those positions;

FIG. 7 illustrates in block diagram form an embodiment of the inventionfor generating a font signal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sketch shown in FIG. 1illustrates the principal components of a partial lineat-a-time printingapparatus of the type shown in the aforementioned U.S. patentapplication Ser. N 0. 734,501. This sketch shows a character belt orcarrier 10 adapted to be driven at a substantially constant speed aroundpulleys or drive Wheels 13-, 14 in a counterclockwise direction asviewed from above. The direction of movement of character belt 10relative to a record medium 12 is such that it traverses a line orproposed line on the record medium. The belt contains a plurality oftype members or flexible fingers 18 each of which includes a type-formedcharacter, numeral, legend, etc., 20 at the upper end thereof. Thecharacter belt 10 may contain one or more sets or fonts of type-formedcharacters.

The record medium 12, which may for example be paper, is driven in thevertical direction. Adjacent to the record medium and aligned across onerow thereof is a typing or inking ribbon 11. A plurality of individualhammers 28 (only four being shown) are spaced apart from the inkingribbon 11 and are similarly aligned across one row of the record medium12. The horizontal position of each hammer'corresponds to a column onthe recording medium that may register one of the available characters.Character belt 10 is driven with the type-formed characters maintainedin alignment between the hammers 28 and the inking ribbon 11. Thus, eachof the characters 20 passes by the face of each of the hammers 28, sothat responsive to appropriate correspondence of a desired characteradjacent a selected column, the appropriate hammer can be actuated byenergization of a respective solenoid 29. When energized, each solenoid29 causes its plunger arm 21 (shown in dotted line) to depress and I0-tate its associated hammer 28 about a pivot axis 23, thereby driving theupper impact head of the hammer against a passing flexible type finger18. The type fingers responds to hammer actuation by deflecting towardthe ribbon, driving the ribbon into the record medium to cause thecharacter to be printed on the record medium at the selected columnlocation.

FIG. 1 also shows a light source 34 and a pair of photosensors 35 and36. Interposed between the light source and the photosensors are thefingers 18 on the character belt and an apertured shield 37. Asexplained hereinafter, light source 34 and the pickup photosensors 35,36 with respectively associated apertures 30 and 31, are used to providea coun signal and a font signal. The character belt has at least onefont of characters arranged in a predetermined sequence. The font andcount signals are effective to indicate registration of the charactersadjacent to a reference location. This indication is derived as follows.Generator 33 responds to the output of photocells 35 and 36 to produce acharacter count and a font signal. The font signal represents thepassage of a special finger which will be described hereafter indicatingthe passage of a particular reference character past a predeterminedprint column position. Following the font signal, each finger passingslot 30 interrupts the light beam from 34 and causes photocell 35 toproduce an odd signal count at the output of photocell 35, and then insubsequently passing the aperture 31 interrupts the light beam again toproduce an even column count signal at the output of photocell 36. Thefont signal, as will be described shortly, is produced in response tothe output of both photocells. The character count and font signalsavailable from 33 are applied to the print command signal source 39.Source 39 responds to the application of input data character signalsfrom a source 40, such as a tape reader, keyboard or incomingtransmission line message, and the output from 33 to produce hammeractuation control signals over cable 23. Source 39 responds to its logiccircuitry and the various inputs supplied thereto to energize respectiveone or more of said solenoids 29 to cause hammer operation and printoutof the proper characters at the desired column positions. Furtherdetails of the operation of the print command signal source andcharacter count and font signal generators will be described hereafter.

As explained relative to the control circuitry in the aforecitedapplication, a circulating shift register memory unit in 39 receives andserially circulates input data character signals. The printer iseffective to generate sum signals which denote the sum of the signalrepresenting the particular finger located at the reference point andthe desired column at which each character is to be printed. The sumsignal is then applied to a comparator where it is compared with each ofthe circulating data character signals in the memory unit and a printcommand signal is generated in response to a coincidence comparison.This print command signal applied over cable 23 controls energization ofthe appropriate solenoid 29 and operation of the associated hammer 28.This is shown in FIG. 1 by the cable 23 interconnecting the printcommand signal source 39 to respective ones of solenoids 29.

In the system disclosed in the aforecited United States patentapplication, it was found desirable to double space the characterfingers 18. In other words, rather than having a character fingerpositioned in accordance with each column on the recording medium, thefingers are spaced to be positioned at every other column. Of course, itis necessary to have hammers for printing at each column position.Accordingly, means must be provided for accommodating the differencebetween the hammer and finger spacing.

In view of the fact that the character fingers are double spaced, itwill be recognized that the sum signals are distinct for one half of thecolumn positions. That is, the sum signal is the same for columns 2 and3, for columns 4 and 5, and every column thereafter. It is thusnecessary to provide means for obtaining the additional informationrequired to separate the odd columns (which may be considered at a firstinstant of time to contain the fingers), from the even columns (which atsaid first instant of time do not contain the fingers). When this isknown, it is possible to energize the comparator outputs to only the oddcolumn hammers during the time that the characters are approaching theodd columns and to energize the outputs to only the even column hammersduring the time that the characters are approaching the even columns.The present invention provides for detecting and indicating thecharacter position and effects the necessary unraveling of the odd andeven conditions to properly control the hammers 28.

As shown in FIGS. 1 and 2, the pickup or detection elements comprise alight source 34 and two photocells 35, 36, respectively located so thatthe fingers 18 intercept the light received by the cells. An apertureplate 37, or similar means, is employed to insure that there is a smallaperture in front of each cell. The signals generated by each cell asthe light impinges thereupon, are utilized to derive all of the othersignals discussed hereinafter in order to effect and initiate thevarious control functions. The two apertures 30 and 31 are spaced sothat the successive signals generated by the passage of a finger 18occur at a time interval corresponding to the passage of one columnwidth. Each finger generates two signals as it passes by the apertures.With reference to the position of the fingers relative to the recordmedium 12 and hammers 28, it will be appreciated that the first signaloccurs as the fingers approach the odd columns and the second signaloccurs \as the fingers approach the even columns. The apertures areprecisely spaced to effect an accurate spacing of the odd-even signalswith no variation for changes in belt speed.

A graphic illustration of the signals that are generated as the fingers18 pass the photocell assembly, may be had by consideration of waveformsA and B in FIG. 4. Each character finger 18 is designed with a widthless than the distance between photocells 35 and 36. In a typicalembodiment, the column width was 0.1 inch, the finger width was 0.09inch and the space between the fingers was 0.11 inch. This relationshipbetween the width of the fingers and the distance between the cellsresults in the energization, i.e., exposure to light, of each cell for alonger period than its disablement. The abscissa of each of thewaveforms A and B represents time and the ordinate thereof representsvoltage. Accordingly, the light on interval is represented by thoseportions of the waveform shown as having a positive voltage. In FIG. 2the fingers 18 are considered to move from left to right. At time t thetrailing edge of a finger may be assumed to uncover the aperture 30 infront of photocell 35. It will be further assumed that at this time, thefingers are approaching the odd columns and accordingly cell 35 will behereinafter referred to as the odd photocell. At time 1 the trailingedge of the same finger will uncover the aperture 31 in front ofphotocell 36. In view of the previous assumptions, the fingers areapproaching the even columns at this time, and accordingly, cell 36 willbe hereinafter referred to as the even photocell. As successive fingers18 pass the photocells, their respective trailing edges will expose thephotocells in the same manner, effecting positive voltage swings at theoutput of odd photocell 35 at times t 1 etc., and at the output of evenphotocell 36 at times t etc.

Obviously, although a single light source 34 has been illustrated in thedrawnig, individual light sources for each photocell may be employed.Still further, it will be appreciated that the photocell sensor assemblymay be positioned in line with finger movements in order to adjust thepoint at which the signals are generated relative to column location.

The manner in which the signals generated by photocells 35 and 36 areused to control the hammer energization circuitry, will be seen byreference to the block diagram in FIG. 5. For brevity, FIG. 5 and thefollowing discussion provides details concerning only the elements thatare germane to this invention. Circuits and units employed in the systemdisclosed in copending application Ser. No. 734,501, are shown bydouble-line blocks in FIG. 5. A thorough understanding of thefunctioning of such circuits is available from said application. Thecapital letters appearing in FIG. 5 indicate that the voltage appearingat that location corresponds to the like designated waveform shown inFIG. 4.

Each output signal from the Photocell Sensors 35 and 36 has its positivegoing excursions differentiated in order to develop a sharply definedpulse commencing at the positive-going portion thereof. This isaccomplished by means of a Differentiation Network 501 for the signalfrom odd photocell 35, and a Differentiation Network 500 for the signalfrom even photocell 36. Waveforms C and D in FIG. 4 are illustrative ofthe signal outputs from the Differentiation Networks 501 and 500,respectively. After differentiation, driving signals are developed byapplying the differentiated pulses to Pulse Width Circuits 503 and 502,respectively. Waveforms E and F in FIG. 4 illustrate the drive pulseoutputs of Pulse Width Circuits 503 and 502. The successive odd drivepulses in waveform E and the successive even drive pulses in waveform F,are each spaced by a time equivalent to the time for movement of thefingers through two column positions. All of the odd drive pulses areoffset in phase from the even drive pulses by a time interval equivalentto the time for movement of a finger from one aperture to the next. Thisis one column width.

The fixed duration of the drive pulses illustrated in waveforms E and Fis used to establish the time interval during which voltage is appliedto the hammer solenoids in order to permit actuation of the appropriatehammer for printing a selected character. It is desired to generate avoltage during either the even or odd timed interval. This isaccomplished by applying the signals from Pulse Width Circuit 503 andPulse Width Circuit 502 to an Electronic Switch 504. Switch 504 isoperative during presence of a drive pulse to connect a regulatedvoltage, identified as +V1, via lead 540 to an Odd Electronic Switch 505and an Even Electronic Switch 506. In the absence of either an odd oreven drive signal, Electronic Switch 504 does not operate and thevoltage on lead 540 is maintained at a lower level as a result of aninterconnection to a voltage designated V4, by means of a resistor 550.The Odd Electronic Switch 505 and its even counterpart 506 are used toapply voltage to respective hammer buses 521 and 522, to which all ofthe solenoid coils of the respective hammers are connected. A suitablecomponent for effecting the desired switching function is a siliconcontrolled rectifier Odd Electronic Switch 505 is operative to apply thevoltage +V1 to odd hammer bus 521 via lead 515. Similarly, EvenElectronic Switch 506 applies the voltage +V1 to even hammer bus 522 vialead 516. The Even and Odd Electronic Switches 506 and 505 are renderedconductive by the output of Differentiation Network 500 and 501,respectively. Thus, it will be seen that each switch applies anoperating voltage to its associated bus in accordance with the signaldeveloped by the respective photosensors. The Electronic Switches 505and 506 are in effect turned on by the differentiated signalsillustrated by waveforms C and D in FIG. 4 and they are turned off(removing power from the hammer solenoids) upon termination of the drivepulses shown by waveforms E and F in FIG. 4.

The odd and the even hammer solenoinds are controlled by circuits thatare similar. The even hammer solenoid circuit may be considered astypical. Even hammer solenoids 524 are each connected from even hammerbus 522 via a resistor 526 and a switching element 528 to a common bus529, which may be grounded. Switching elements 528 are shown as siliconcontrolled retcifiers having their control electrodes connected to aColumn Decoder 560. The Column Decoder is fully disclosed and discussedin the aforecited patent application Ser. No. 734,501. It determineswhich hammers are to be actuated in order to print appropriatecharacters in desired columns on the record medium. The determination isindicated by the development of a triggering pulse on the lead connectedto the control electrode of the appropriate controlled rectifier. By wayof refinement, the response time of the various hammer solenoids isincreased by providing resistors 526. In addition, to provide for decaycurrent in a solenoid, unidirectional conducting devices 541 and 542 areprovided between a voltage source V3 and the odd and even hammer buses,respectively. The relative magnitudes of the various voltage levelsreferred to, will be apparent from FIG. 4.

In addition to initiating control over the hammer soleonids, thedifferentiated signals shown as waveforms C and D in FIG. 4, are appliedto a Comparison Generator 510. Comparison Generator 510 develops twosignals after a slight time delay. These signals are designated ODDCOMPARE and EVEN COMPARE. They are illustrated by waveforms H and I inFIG. 4. They are used in order to control two circuits which are morefully described in the aforecited copending patent application.

First, the output signals from Comparison Generator 510 are compared inan Odd-Even Comparator 570 with a column signal representing the columncurrently being processed. If the column signal indicates that an oddcolumn is involved and the ODD COMPARE signal is present, the InputData-Belt Character Comparator 580 shown in the copending application isenabled. If neither of the above conditions exists, the Comparator 580is disabled. As explained in said application, since the Comparator 580controls the Column Decoder 560, trigger signals will be applied to thesilicon controlled rectifier gates only when the Comparator 580 is bothenabled and indicates a comparison between stored data and characterpositioning.

The EVEN COMPARE AND ODD COMPARE signals from Comparison Generator '510are also used to con trol further Electronic Switches 508, 507 which areconnected to the even and odd buses, respectively. These switches may bein the form of transistors and when the voltage on lead 540 is lowerthan +V1, they are not operable. Electronic switches 507 and 508 areused to sustain conduction of the hammer control silicon controlledrectifiers 527, 528, but not trigger them. For example, during theinterval when the ODD COMPARE signal is present, Comparator 580 isenabled to odd column numbers. Whenever coincidence in the Comparator580 occurs, the resulting decoded column signal is applied via ColumnDecoder 560 to the control electrode of the appropriate odd SCRs 527,causing them to conduct. Similarly, during EVEN COMPARE intervals,decoded signals are applied to the control electrodes of the appropriateeven SCRs 528. The controlled rectifiers perform the function of shorttime memory devices, storing column information in the individual hammercircuits during the compare interval.

The waveforms J and K in FIG. 4 show the composite efifect of thevarious voltages applied to odd bus 521 and even bus 522, respectively.During the compare interval, when +V2 is applied to the buses viaElectronic Switches 507, 508, various control electrodes will receivesignals from Column Decoder 560, and a small holding current flows inthe hammer coils 523, 524 whose controlled rectifiers have receivedsignals. At termination of the compare interval, the voltage -+V1 isapplied and a large current flows in these coils. A short intervallater, the hammers strike the fingers which have moved into columnposition. During the interval when neither +V1 nor +V2 is applied,energy is removed from the coils and the voltage of the hammer buses521, 522 decreases to -V3 (a voltage more positive than V4). Rectifiers519 and 520 function to isolate voltage supply of +V2 during theinterval when the voltage supply of +V1 is being applied to the buses.

For a more complete understanding of the operating sequence hereinbeforedescribed, reference is made to FIG. 6. In this figure, a chart ispresented illustrating the position of the various character fingers atdifferent pe riods in time.

At time t the fingers of the character belt are assumed to be in theapproximate positions shown with respect to columns 1 through 6 on therecord medium. At this initial instant of time, the ODD COMPARE signalbegins and the Input Data-Belt Character Comparator 580 is enabled toodd column numbers. Thus, if comparison is found during this interval,Column Decoder 560 permits its output to apply triggering signals to thecontrol electrode of the appropriate controlled rectifier 527 associatedwith the odd column in which printing is to take place. This may occurseveral times during the ODD COM- PARE period, and accordingly severalodd controlled rectifiers 527 may be triggered into conduction.Excitation voltage has been applied to the coils 524 of the evenhammers, but this will not be considered for the mo merit. As indicatedin FIG. 6, character B is moving to the next odd column 1, letter C ismoving to column 3, letter D is moving to column 5, etc. If B is to beprinted in column 1 and D is to be printed in column 5, controlledrectifiers (1) and (5) would receive signals and holding current wouldflow due to voltage +V2 which was applied at time t During the intervalfrom t to I decoding occurs and the characters move to the approximatepositions illustrated. At time 1 odd comparison terminates and thevoltage l-Vl is immediately applied to the odd hammer bus 521. Currentflows in those coils 523 with controlled rectifiers 527 that have beenmade conductive. Accordingly, the respective hammers begin movement.

At time t the Column Decoder 560 adjusts its output to apply appropriatecontrol signals to the even controlled rectifiers 528 in the same mannerdescribed relative to the odd hammer circuits. At time voltage isremoved from odd bus 521. The hammers are in flight at this point andinertia keeps them moving even though power is removed. At this instantthe hammers are close to the fingers but in a preferred embodiment theyhave not yet made contact.

At time 12;, even comparison terminates and the voltage +Vl is appliedto the even hammer bus 522. An instant later, when the characters arealigned with each column, the odd hammers make contact with the fingerswhich have advanced from the initial positions shown at time t and thetypeface drives the ribbon onto the record medium.

The distance of the characters from the odd column locations at time twhen voltage +Vl is applied, is equal to the product of the fingervelocity and the response time of the hammer. The photocell assembly isproperly positioned so that voltage +V1 is applied when the fingers areat the correct distance from the column position to effect proper hammeractuation and printing. At time i odd comparison begins again and theaforedescribed sequence of operations is repeated.

In addition to utilizing the photocell assembly for generating signalseach time a finger passes, it is possible to use this same assembly togenerate a font signal representative of a particular position of acharacter belt and/ or the beginning of a font of characters. Asdescribed above, the width of the fingers 18 is normally narrower thanthe space between them. Thus, the interval when each photocell is darkis shorter than the interval when it receives light. Furthermore,because the photocell apertures are spaced approximately 0.1 inch apart,which is greater than the finger width, there is never a condition whenboth cells are dark at the same time.

In accordance with a further feature of the invention, one of thefingers 18 is increased in width at its leading edge in order to producea dark interval of the photocells that is longer than the lightinterval. The increase in Width may be for example from 0.09 inch to0.13 inch. This condition is illustrated in finger 22 in FIG. 3.Waveforms L and M in FIG. 4 illustrate the signals which occur as thesingle wide finger passes the photocells. It will be noted that thereare two intervals when both photocells are dark, i.e., at zero voltage,at the same time. The first dark interval occurs when the leading edgeof the wide finger 22 covers the odd photocell 35. At this time thetrailing edge of the preceding finger also covers the even photocell 36.The second dark interval occurs a short time later when the wide finger22 has advanced to the illustrated position where it covers bothphotocells. The odd-even signals can be applied to suitable logiccircuitry to generate a discrete signal for either one of the darkintervals. To make this a fontf signal, it is simply necessary to widenthe appropriate finger.

With specific reference to the system described in the aforecited patentapplication, a font signal may be generated by the inclusion of aflip-flop as shown in FIG. 7. The signal from even photocell 36 is usedas a steering signal to the flip-flop, and the flip-flop is triggeredonly when the output of the odd photocell 35 reflects a change from darkto light. This arrangement assures that the flipflop will function toproduce a discrete font signal from the second dark interval.

Referring to FIG. 7 when both photocell signal sources 600 and 601 areilluminated or one is darkened and the other is illuminated, theflip-flop 602 is in the reset state, and no control signal is sent overlead 603 to the utilization device 604. In a particular embodiment 600and 601 comprised photocells 36 and 35 respectively, and 604 comprised afinger counter. Ordinarily each of the fingers 18 has at least one ofits edges, the trailing edge in a particular embodiment, preciselylocated with respect to the same edges of the other fingers and having awidth which precludes simultaneously darkening both photocells 35 and36. In view of the latter flip-flop 602 is precluded from operatingdevice 604. However, if one of the fingers, say 22 shown in FIG. 3 isbroadened to permit simultaneous darkening of both photocells the evenphotocell cell circuit sends a set signal to flip-flop 602. Then whenthe odd photocell goes from darkened to illuminated, a signal is sent to604. In a particular embodiment 604 comprised a finger counter, and theflip-flop output signal reset the counter to a reference count,indicating the beginning of a finger count. For further details of theembodiment reference can be made to FIG. 6 of the aforementionedapplication wherein the finger counter is reset to a count of 32. Thusonly when one of the sensors, say the odd sensor, goes from darkened toilluminated in the presence of a darkened other sensor, i.e., evensensor, is a utilization signal produced and delivered to a utilizationdevice. After the device 604 has been reset to its predetermined countstate, a reset signal is delivered from 604 over 605 to 602.

It should be noted that in the particular embodiment described, theprecisely located trailing edge of the fingers was employed to initiatethe hammer drive signals, both odd and even hammer drives, and a comparesignal occurring between hammer drive signals and just prior to theinitiation of a drive signal. An extension of the other or leading edgeof one of the fingers provides the change in font signal. These resultsoccur since the normal finger width is less than the spacing betweenaperture centers where the aperture center spacing is equal to thecolumn center spacing. The wide finger, however, has a width which isgreater than the spacing between aperture centers which permits bothphotocells to be darkened concurrently and thereby to provide adistinguishing and therefore useful signal.

It should be noted that in other applications, the particular edgesemployed may be interchanged and their functions may dilfer withoutdeparting from the spirit of the invention.

It will be appreciated that increasing the width of a finger at itsleading edge does not interfere with normal operation because all othersignals are initiated at the trailing edge of each finger as it uncoversthe apertures and permits light to reach the photocells. Of course, itis only necessary to increase the width of the fingers at the portionthat intercepts the light beam.

Although a particular embodiment of the invention has been shown anddescribed, it Will be appreciated that the applicant intends to includeall those modifications which come within the spirit and teachings ofthe invention. By way of example only, it should be understood thatalthough optical means have been described for detecting passage ofelements, other means may be employed. Thus, magnetic principles may beadopted by using magneto fingers and magnetic sensors having theirpoints of sensing action positioned along the print line and spacedapart the requisite number of print column positions. A magnetic fluxsystem employing non-magnetic fingers could also be used. An oscillatormight generate a high frequency magnetic field in the path of thefingers. Suitably located 10 pickup coils in the flux field would thenhave a change in induced voltage as the fingers passed through thefield. Of course, the invention is also adapted for use with printingsystems and apparatus differing from that of the oft-cited applicationSer. No. 734,501.

While the optical elements have been shown on the side of the beltremote from the hammer location, it should be recognized that otherlocations may be more suitable. For example, the elements could belocated on the hammer side of the belt and even entered along the lineof type.

All arrangements falling within the fair meaning and scope of thefollowing claims are intended to be included within this invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A printer comprising a plurality of type members mounted upon aflexible type carrier means, said type carrier being movable along aprint line having a plurality of spaced print positions, a plurality ofselectively operable hammer means positioned along said print line forstriking said type members at said print positions to cause printingalong said print line at even and odd print column positions, each ofsaid hammer means spanning a respective print column position, said typemembers having their centers uniformly spaced apart a distance equal totwice the distance between the centers of adjacent hammer means, firstand second sensors positioned along said print line and spaced apart adistance equal to the distance between the centers of an odd number ofprint column positions, means to advance said type carrier means alongsaid print line, means for supplying coded data to be printed, meansresponsive to one of said sensors for providing a first signal inresponse to the type bearing [fingers coinciding with a given alignmentwith the odd print column positions, means responsive to the other ofsaid sensors for providing a second signal in response to the typebearing fingers coinciding with a given alignment with the even printcolumn positions, means responsive to both of said sensors to provide athird signal indicating the instantaneous position of the type carriedby said carrier in relation to the columns of said print line, meansresponsive to said first, second and third signals for providing a codedsignal denoting each of said plurality of said type members aligned forprinting at desired print column positions, means for comparing saidsupplied coded data to be printed at particular print column positionsand said provided coded signal for the type members aligned at desiredprint column positions, and means responsive to a given compare signalto actuate the proper hammer means to print the supplied characters atthe selected print positions.

2. An arrangement according to claim 1 wherein said means for supplyinga coded signal denoting each of said plurality of type members alignedfor printing comprises a circulating column counter.

3. A position sensing system for printing symbols in response to inputdata along a print line having a plurality of alternately spaced odd andeven print column positions comprising a plurality of type fingers,means for moving each of said type fingers in series to successivelytraverse all of the print column positions associated with saidpredetermined print line, said fingers having their centers uniformlyspaced apart a distance equal to an integral multiple of twice thedistance between the centers of adjacent print column positions, firstand second sensors positioned along said print line and spaced apart adistance which is a function of the distance between the centers ofadjacent print column positions, one of said sensors providing a firstsignal in response to the type fingers coinciding with a given alignmentwith one of said odd or even print column positions, the other of saidsensors providing a second signal in response to the type fingerscoinciding with a given alignment with the other of said odd or evenprint column positions, and print control means responsive to said firstand second signals to enable operation of 1 1 desired type bearingfingers to effect printing in accordance with input data at one and theother of said odd or even print column positions respectively.

4. A system according to claim 3 wherein each of said sensors comprisesa photosensitive means and associated apertured plate, a light source isdisposed in a position to illuminate said photosensitive means throughits associated apertured plate, and the path of said type fingers lyingbetween said light source and said photosensitive means.

5. A system according to claim 3 wherein said fingers have a Width inthe direction of finger movement which is less than the width of acolumn position.

6. A system according to claim 5 wherein at least the same one edge ofeach finger is precisely located relative to all other fingers and saidfirst and second sensors detect passage of said edge to generate a firstor second signal respectively.

7. A system according to claim 6 wherein a selected finger has a widerconfiguration at the other edge and said first and second sensorssimultaneously detect passage of both edges of said selected finger togenerate a third signal defining the column location of said series oftype fingers.

8. An arrangement according to claim '3 wherein said sensors comprisemeans for transmitting light to said sensors through the spaces betweensaid fingers and said sensors successively sense light interruption byeach finger traversing said print line.

9. An arrangement according to claim 3 further comprising means forproducing a front signal establishing the instantaneous position of thetype carried by said fingers in relation to the columns of said printline comprising the width of said one of said fingers being dimensionedto be greater than one column width, said sensors responsive to thepassage of said one finger past said sensors simultaneously to provide athird signal, and means responsive to said first and second' signals andsaid font signal for enabling selected ones of said type fingers toefiect printing in accordance with input data at one and the other ofsaid odd or even print column positions respectively.

10. A printer comprising a plurality of type members representing aplurality of fonts mounted upon a flexible type carrier means, said typecarrier being movable along a print line having a plurality ofalternately spaced even and odd print column positions, a plurality ofselectively operable hammer means positioned along said print line forstriking said type members at said print column positions to causeprinting along said print line at said even and odd print columnpositions, each of said hammer means spanning a respective print columnposition, said type members having their centers uniformly spaced aparta distance equal to twice the distance between the centers of adjacenthammer means, first and second sensors having their points of sensingaction positioned along said print line and spaced apart a distanceequal to the distance between the centers of adjacent print columnpositions, means to advance said type carrier means to move each of saidtype members to traverse all of the print columns associated with saidprint line, means for supplying coded data to be printed, meansresponsive to said first sensor for providing an odd column positionsignal in response to the type members coinciding with a given alignmentwith said odd print column positions, means responsive to said secondsensor for providing an even column position signal in response to thetype bearing fingers coinciding with a given alignment with said evenprint column positions, means responsive to both of said sensors toprovide a third signal indicating the instantaneous position of thefonts of type carried by said carrier in relation to the columns of saidprint line.

11. An arrangement according to claim comprising means responsive tosaid even and odd column position signals to selectively operate saidhammer means to only cause printing at said odd or even print columnpositions 12 respectively, and means responsive to said third signal toestablish the font of type to be printed.

12. A position sensing system operative to establish the preciselocation of individual type bearing fingers mounted upon a carrier suchthat movement of the carrier along a print line causes each of thefingers to successively traverse all of the print column positionsassociated with said line, said fingers having a width in the directionof carrier movement less than column width, said fingers being uniformly spaced apart a distance equal to twice the distance between thecenters of adjacent print column positions, first and second sensorshaving their points of sensing action positioned along said print lineand spaced apart a distance equal to the distance between the centers ofan odd number of print column positions, said first sensor responsive tofingers coinciding with a given alignment with odd numbered ones of saidprint column positions to provide a first signal, said second sensorresponsive to the fingers coinciding with a given alignment with evennumbered ones of said print column positions to provide a second signal,and means responsive to said first and second signals to enable saidfingers to alternately print along said print line at odd and evennumbered ones of said print column positions respectively.

13. A position sensing system operative to establish the preciselocation of individual type bearing fingers mounted upon a carrier suchthat movement of the carrier along a print line causes each of thefingers to successively traverse all of the print column positionsassociated with said line, said fingers having a width in the directionof carrier movement less than a column Width, said fingers beinguniformly spaced apart a distance equal to twice the distance betweenthe centers of adjacent print column positions, first and second sensorshaving their points of sensing action positioned along said print lineand spaced apart a distance equal to the distance between the centers ofadjacent print column positions, said first sensor responsive to fingerscoinciding with a given alignment with odd numbered ones of said printcolumn positions to provide a first signal, said second sensorresponsive to the fingers coinciding with a given alignment with evennumbered ones of said print column positions to provide a second signal,at least one of said fingers having its Width extended in one directionof carrier movement to cause said first and second sensors to respondsimultaneously with a given alignment of said one finger with bothsensors to provide a third signal, and means responsive to said first,second and third signals to enable said fingers to alternately printalong said print line at odd and even numbered print column positions.

14. A position sensing system operative to establish the preciselocation of individual type bearing fingers mounted upon a carrier suchthat movement of the carrier along a print line causes each of thefingers to successively traverse all of the print column positionsassociated with said line, said fingers having a Width in the directionof carrier movement less than column Width, said fingers being uniformlyspaced apart a distance equal to twice the distance between the centersof adjacent print column positions, first and second sensors havingtheir points of sensing action positioned along said print line andspaced apart a distance equal to the distance between the centers ofadjacent print column positions, said first sensor responsive to thetrailing edge of moving fingers coinciding with a given alignment withthe odd numbered ones of said print column positions to provide a firstsignal, said second sensor responsive to the trailing edge of movingfingers coinciding with a given alignment with the even numbered ones ofsaid print column positions to provide a second signal, at least one ofsaid fingers having its width extended in the direction of carriermovement to cause said first and second sensors to respondsimultaneously with a given alignment of said one fingers with bothsensors to provide a third signal, and means responsive 13 to saidfirst, second and third signals to enable said fingers to print alongsaid print line.

15. A position sensing system operative to establish the preciselocation of individual type bearing fingers mounted upon a carrier suchthat movement of the carrier along a print line causes each of thefingers to successively traverse all of the print column positionsassociated with said line, said fingers having a width in the directionof carrier movement less than column width, said fingers being uniformlyspaced apart a distance equal to twice the distance between the centersof adjacent print column positions, first and second sensors havingtheir points of sensing action positioned along said print line andspaced apart a distance equal to the distance between the centers ofadjacent print column positions, said first sensor responsive to eachfinger successively coinciding with a given alignment with an oddnumbered one of said print column positions to provide a train of oddcolumn position signals, said second sensor responsive to eachfingersuccessively coinciding with a given alignment with an evennumbered one ofsaid print column positions to provide a train of evencolumn position signals, and said first and second sensors responsive toa further finger coin- 14 ciding simultaneously with a given alignmentwith an even numbered and an odd numbered one of said print columnpositions to provide a start of font signal.

References Cited UNITED STATES PATENTS 2,787,953 4/1957 Sobisch et a1101-93RC 2,906,200 9/1959 Pfleger 101-93RC 2,936,704 5/1960 Hense101--93RC 3,007,399 11/1961 Sasaki et al 101111X 3,220,343 11/1965Wasserman 1011l1X 3,303,775 2/1967 Giannuzzi 101-93RC 3,342,127 9/1967Pitt 101-93RC 3,416,442 12/1968 Brown et a1. 101-93RC 3,420,164 1/ 1969Lee 101-93RC WILLIAM B. PENN, Primary Examiner E. M. COVEN, AssistantExaminer US. Cl. X.R. 101--1 11 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 3,605,610 Dated September 20, 1971 Inventor(s)Earle B. McDowell, Clifford M. J nes and Seymour M. DePuy It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 53, cancel "fingers" and insert finger Column 4 line 19,cancel 'conut" and insert count Column 5, line 43, cancel "drawnig" andinsert drawing Column 6, line 29, after "rectifier" insert a period.Column '7, line 17, cancel "AND" and insert and Column 9, line 69,cancel "magneto" and insert magnetic Column 11, line 30, cancel "front"and insert font Column 12, line 69, cancel "fingers" and insert fingerSigned and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GO'ITSCHALK Attesting Officer Commissionerof Patents DRM PC4050 (10'69) USCOMM-DC scan-Poe U 5 GOVERNMENT PRINTINGOFFICE: I969 O-Jfifl-Sll

